No start condition: Help me figure out what's left...

My66dodge · **Posted:** Thu Feb 14, 2019 12:41 am

I have replaced many fQS's on Duramax's and MANY cp3's on them too, the cummins CP3 almost never fail, they are different than the ones on the jeep and Duramax, the jeep and Duramax both have a built in lift pump function on the cp3 they use. The failure point comes most often when pushed hard with a filter that is restricted. I did 3 just last year, ususaly when they fail they explode internally or invert the seal and either way they end up leaking. The pump that has the high failure rate is the CP4, they are real crap, I did 5 last year, 2 on ecodiesels and the rest were Duramax's where I did the industrial injection cp4 to cp3 conversion.

Mountainman · **Posted:** Thu Feb 14, 2019 11:35 am

My66dodge wrote:

I have replaced many fQS's on Duramax's and MANY cp3's on them too, the cummins CP3 almost never fail, they are different than the ones on the jeep and Duramax, the jeep and Duramax both have a built in lift pump function on the cp3 they use. The failure point comes most often when pushed hard with a filter that is restricted. I did 3 just last year, ususaly when they fail they explode internally or invert the seal and either way they end up leaking. The pump that has the high failure rate is the CP4, they are real crap, I did 5 last year, 2 on ecodiesels and the rest were Duramax's where I did the industrial injection cp4 to cp3 conversion.

Interesting, This has me wondering if the OP had any bucking, like I've experienced with a clogged filter? I would definitely be more suspect of the the CP3 if so.
I think we dont have the kind of stress that a hungry Duramax puts on a pump, but our pumps aren't getting any younger, and likely more fragile plastic pistons as well. It would be amazing if they lasted 500k though, time will tell.

WWDiesel · **Posted:** Thu Feb 14, 2019 12:30 pm

Mountainman wrote:

My66dodge wrote:

I have replaced many fQS's on Duramax's and MANY cp3's on them too, the cummins CP3 almost never fail, they are different than the ones on the jeep and Duramax, the jeep and Duramax both have a built in lift pump function on the cp3 they use. The failure point comes most often when pushed hard with a filter that is restricted. I did 3 just last year, ususaly when they fail they explode internally or invert the seal and either way they end up leaking. The pump that has the high failure rate is the CP4, they are real crap, I did 5 last year, 2 on ecodiesels and the rest were Duramax's where I did the industrial injection cp4 to cp3 conversion.

Interesting, This has me wondering if the OP had any bucking, like I've experienced with a clogged filter? I would definitely be more suspect of the the CP3 if so.
I think we dont have the kind of stress that a hungry Duramax puts on a pump, but our pumps aren't getting any younger, and likely more fragile plastic pistons as well. It would be amazing if they lasted 500k though, time will tell.

More reason than ever to have a way of monitoring fuel pressure feeding the CP3 especially if you have a lift pump and / or a 2 micron fuel filter as dgeist stated he does.
Fuel starvation during aggressive driving or at any time for that matter can be detrimental to an injection pump that relies solely on diesel fuel through it's internals for lubrication. :grim:

I have pressure gauges on both my Jeep & Dodge Cummins to monitor fuel pressure leaving the 2 micron fuel filter and entering the injection pumps as pictured below.

GordnadoCRD · **Posted:** Thu Feb 14, 2019 2:48 pm

WWDiesel wrote:

More reason than ever to have a way of monitoring fuel pressure feeding the CP3 especially if you have a lift pump and / or a 2 micron fuel filter as dgeist stated he does.
Fuel starvation during aggressive driving or at any time for that matter can be detrimental to an injection pump that relies solely on diesel fuel through it's internals for lubrication. :grim:

I have pressure gauges on both my Jeep & Dodge Cummins to monitor fuel pressure leaving the 2 micron fuel filter and entering the injection pumps as pictured below.

You are running the drop-in retrofit in-tank lift pump, 8-12 psi, correct?
What numbers does the Jeep indicate while driving / accelerating / towing / etc?

WWDiesel · **Posted:** Thu Feb 14, 2019 4:37 pm

GordnadoCRD wrote:

WWDiesel wrote:

More reason than ever to have a way of monitoring fuel pressure feeding the CP3 especially if you have a lift pump and / or a 2 micron fuel filter as dgeist stated he does.
Fuel starvation during aggressive driving or at any time for that matter can be detrimental to an injection pump that relies solely on diesel fuel through it's internals for lubrication. :grim:

I have pressure gauges on both my Jeep & Dodge Cummins to monitor fuel pressure leaving the 2 micron fuel filter and entering the injection pumps as pictured below.

You are running the drop-in retrofit in-tank lift pump, 8-12 psi, correct?
What numbers does the Jeep indicate while driving / accelerating / towing / etc?

Yes on the drop intank pump
~13-14 key on, ~11-12 engine started at idle
Hard acceleration or towing under power it can drop to ~7-8
Never seen it drop below 5 under any conditions
But temperature of fuel does have an big impact on pressures, cold fuel will lower pressures by a few lb.s until it warms up a bit by recirculating.

GordnadoCRD · **Posted:** Thu Feb 14, 2019 6:47 pm

So a normal pressure drop under acceleration / towing conditions is somewhere around 5 psi.
If the gear pump inside the CP3 were working alone, this translates to roughly 10 1/4 inches of mercury. That's quite a fair amount, (half of it's total ability) and presumably with good lines and clean filters.
Cold weather, used filters, and fittings not designed for vacuum being "normal", it's obvious to see how easily they suffer aeration problems in the fuel.

dgeist · **Posted:** Thu Feb 14, 2019 8:00 pm

It lives!!!

SO, another forum member in the area recommended a tdi mechanic he's used. I got a tow up on Monday morning and gave the full run-down of everything I'd done. He agreed with all the things that were tried and went to work. After a day or two waiting on the jobs in front of me(small shop) and a couple back and forths on the phone, he thought that it might have simply jumped time due to it sounding so bad on crank. I told him the CRD always sounds that bad, then, on a hunch he called a buddy to look all around with a bright flash light while it was cranking and violla! There was a tiny leak at the fuel temp port (opposite the output) that was letting in (and out) air and fuel and was preventing the CP3 from being able to self-purge all the bubbles and generate pressure. I was getting plenty of fuel, but apparently after I changed the filter, there was just a LITTLE to much air to self-purge and the small leak didn't help Once the temp sensor fitting was tightened and it was bled (cranked) for about 20 seconds, it fired and all readings we're good.

Long story short, I feel like a dolt for missing a leak in the very first place I checked (fuel head) but am happy to have things running again and to have found a honest diesel mechanic who only charged me for a few labor hours and the cost of a bottle of liqui-moly diesel-purge, which he apparently always uses as a rule on any fuel system work.

Dan

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Mountainman · **Posted:** Fri Feb 15, 2019 12:57 am

Wow, glad it's back on the road, congrats!

WWDiesel · **Posted:** Fri Feb 15, 2019 8:32 am

dgeist wrote:

It lives!!!
SO, another forum member in the area recommended a tdi mechanic he's used. I got a tow up on Monday morning and gave the full run-down of everything I'd done. He agreed with all the things that were tried and went to work. After a day or two waiting on the jobs in front of me(small shop) and a couple back and forths on the phone, he thought that it might have simply jumped time due to it sounding so bad on crank. I told him the CRD always sounds that bad, then, on a hunch he called a buddy to look all around with a bright flash light while it was cranking and violla! There was a tiny leak at the fuel temp port (opposite the output) that was letting in (and out) air and fuel and was preventing the CP3 from being able to self-purge all the bubbles and generate pressure. I was getting plenty of fuel, but apparently after I changed the filter, there was just a LITTLE to much air to self-purge and the small leak didn't help Once the temp sensor fitting was tightened and it was bled (cranked) for about 20 seconds, it fired and all readings we're good.
Long story short, I feel like a dolt for missing a leak in the very first place I checked (fuel head) but am happy to have things running again and to have found a honest diesel mechanic who only charged me for a few labor hours and the cost of a bottle of liqui-moly diesel-purge, which he apparently always uses as a rule on any fuel system work.
Dan

Glad you got it back running!
Just curious, did you fail to fill the new filter with fuel and then bleed out remaining air since you have an in-tank pump? :shock:

dgeist · **Posted:** Fri Feb 15, 2019 8:53 am

WWDiesel wrote:

Glad you got it back running!
Just curious, did you fail to fill the new filter with fuel and then bleed out remaining air since you have an in-tank pump? :shock:

I didn't pre-fill but I did check during the troubleshooting and it looked full (in the center). Not sure if that's the unfiltered or clean side. It might not have been able to fully purge if there was a small leak just downstream. The CP3 suction pump was probably doing mostly fine with the old filter but was sucking in bubbles after the head was drained.

Dan

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WWDiesel · **Posted:** Fri Feb 15, 2019 8:57 am

dgeist wrote:

WWDiesel wrote:

Glad you got it back running!
Just curious, did you fail to fill the new filter with fuel and then bleed out remaining air since you have an in-tank pump? :shock:

I didn't pre-fill but I did check during the troubleshooting and it looked full (in the center). Not sure if that's the unfiltered or clean side. It might not have been able to fully purge if there was a small leak just downstream. The CP3 suction pump was probably doing mostly fine with the old filter but was sucking in bubbles after the head was drained.
Dan

But didn't you say you have an intank pump?
I would think that would force any air out any leak point???

dgeist · **Posted:** Fri Feb 15, 2019 9:28 am

WWDiesel wrote:

But didn't you say you have an intank pump?
I would think that would force any air out any leak point???

I do... and I was thinking the same thing. The Mechanic did say he was getting some leakage at that fitting and tightening it fixed the issue. Now that you mention it, leaking OUT would make more sense. I need to go back and diagram out which side of the filter flow my temp sensor is so I can keep i straight in my head and also not dork it up next time.

Regardless...lots of leaking and draining and bleeding going on under there during the whole process. I need to rinse the whole engine bay out with some mild degreaser before I put it back in the garage and stink up the place

WWDiesel · **Posted:** Fri Feb 15, 2019 11:22 am

dgeist wrote:

WWDiesel wrote:

But didn't you say you have an intank pump?
I would think that would force any air out any leak point???

I do... and I was thinking the same thing. The Mechanic did say he was getting some leakage at that fitting and tightening it fixed the issue. Now that you mention it, leaking OUT would make more sense. I need to go back and diagram out which side of the filter flow my temp sensor is so I can keep i straight in my head and also not dork it up next time.

Regardless...lots of leaking and draining and bleeding going on under there during the whole process. I need to rinse the whole engine bay out with some mild degreaser before I put it back in the garage and stink up the place

By installing the 2 micron secondary filter a few years ago, it allowed me to have a bleed valve for priming and removing all the air out of the filters when I change them.
I simply cycle the key on and off a couple of times, ~20 seconds between each cycle, and the intank pump totally bleeds all air out of the filters and / or system.

Picture below shows bleed valve and hard plastic tube I use to vent into a container outside of vehicle to keep things nice and clean under the hood. :BANANA:

dgeist · **Posted:** Fri Feb 15, 2019 4:07 pm

WW, I had a similar needle valve installed in my old ( original) fuel head with the cat thread adapter. I used to have to bleed and pump that all the time. I think I may transfer it over to the fm100 now just for some piece of mind.

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My66dodge · **Posted:** Fri Feb 15, 2019 11:10 pm

Glad to hear it is running again, glad to hear it was a simple fix. That's why at my shop I NEVER give over the phone diagnosis, so many times it is the things you can't SEE over the phone lol

I have plans to add the 2 micron secondary filter to mine when I do the in tank pump. I have an extra raptor pump from a 24v sitting around I was thinking of putting in but I think the carter will be more reliable. I plan to have a digital fuel pressure gauge installed at that time. I am in the process of making a 4 gauge pod for the dash to mount above the vents, I am working on doing it in fiberglass. Things I am building myself have slowed to a crawl with the whole taking over a shop thing, things have been very busy, that's why I try to delicate builds to my vendors.

WWDiesel · **Posted:** Sat Feb 16, 2019 10:10 am

My66dodge wrote:

Glad to hear it is running again, glad to hear it was a simple fix. That's why at my shop I NEVER give over the phone diagnosis, so many times it is the things you can't SEE over the phone lol
I have plans to add the 2 micron secondary filter to mine when I do the in tank pump. I have an extra raptor pump from a 24v sitting around I was thinking of putting in but I think the carter will be more reliable. I plan to have a digital fuel pressure gauge installed at that time. I am in the process of making a 4 gauge pod for the dash to mount above the vents, I am working on doing it in fiberglass. Things I am building myself have slowed to a crawl with the whole taking over a shop thing, things have been very busy, that's why I try to delicate builds to my vendors.

If you want a custom mount for a secondary fuel filter (w/down brace 05 only) for a fuel filter head like the Wix 24770 or NAPA 4770, I can supply them. All simple bolt on!
PM if interested.

My66dodge · **Posted:** Sat Feb 16, 2019 10:19 am

Looks good, that's the fuel filter head I had in mind, I use it with an electric transfer pump and 2 micron filter to dispose of my used ATF, I have several 12v and 7.3 guys who stop by and fill up with it... It runs great and since it burns hotter the obs 7.3 boosts faster

No start condition: Help me figure out what's left...

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